Protective coating and method of using such coating

ABSTRACT

A vehicle masking material and method of use. The masking material in one embodiment includes polyvinyl alcohol, ethyl alcohol, glycerine or triethylene glycol, a surfactant, and water. The masking material is applied to a surface which is to be protected from paint overspray or other mechanical process, allowed to dry, and paint is applied. After drying of the paint, the masking material is removed by peeling or water washing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.07/972,037, filed on Nov. 05, 1992 and now U.S. Pat. No. 5,302,413 whichis a continuation-in-part of U.S. application Ser. No. 07/614,330 filedon Nov. 16, 1990 and now abandoned which is incorporated herein byreference for all purposes.

BACKGROUND OF THE INVENTION

The present invention relates to the field of protective coatings to beused during mechanical processing operations of vehicles or buildings.More specifically, in one embodiment the invention provides an improvedmethod and composition for masking selected portions of a vehicle frompaint.

It is well known that painting operations often require masking ofcertain portions of the vehicle or building to prevent overspray. Forexample, it is often necessary to mask trim and windows on a vehiclefrom paint overspray. Also, building stucco must frequently be protectedfrom paint or primer coats. On occasion, it is necessary to mask paintedportions of a vehicle or building from paints of a different color andoverspray of paints of the same color. It is also well known that manysurfaces are susceptible to marring and scratching during mechanicalprocessing operations on proximate surfaces. For example, welding andgrinding can have deleterious effects on surrounding surfaces.

In practice, masking operations are often one of the most time consumingand, therefore, expensive parts of the painting process. In spite ofattempts to develop suitable chemical masks for vehicle painting,vehicle painters continue to use primarily masking tape and paper tocover portions of a vehicle where paint is not desired. To mask the trimon a car, for example, will often require many hours of tedious labor.Furthermore, even when done carefully, defects in such paint masks allowpaint to contact surfaces which are desired to be protected.

Solutions have been proposed to the problem of protecting surfacesduring mechanical processing operations. However, such techniques haveoften not found extensive use. Some of the proposed chemical masks havebeen unsuitable for application to portions of a vehicle or buildingbecause of damage which would potentially occur to the protectedportions of the vehicle or building. Other compositions are not watersoluble. This causes particular problems because environmental controlsof solvents are becoming stricter with time. Other compositions aredifficult to apply, difficult to remove, excessively costly, or thelike.

From the above it is seen that an improved masking composition isneeded.

SUMMARY OF THE INVENTION

An improved masking composition and method is provided by virtue of thepresent invention. The method includes the steps of applying asubstantially continuous film of a masking material on a vehicle,building, or other work surface to be protected during a "mechanicalprocessing operation". Such operations include, for example, painting,grinding, welding, and etching. These steps may be performed, forexample, during an assembly line production of a vehicle. By "building"it is intended to mean herein a house, warehouse, apartment, garage,store, or the like. By "vehicle" it is intended to mean herein a car,boat, plane, train, railroad car, or the like. By "substantiallycontinuous film" it is intended to mean herein a film lacking pinholesthrough which paint or other materials generated during mechanicalprocessing could reach an underlying surface. The masking material is,in one specific embodiment, a composition of water, an aliphatic polyol,alcohol, and a surfactant. In a different embodiment the maskingmaterial includes water, a plasticizer (such as glycerine, triethyleneglycol or polyethylene glycol), an aliphatic polyol, alcohol andsurfactant. The masking material will dry quickly, and be readilyremovable with water after use. Further, the material is relativelyharmless from an environmental point of view.

A further understanding of the nature and advantages of the inventionsherein may be realized by reference to the remaining portions of thespecification.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an improved method and composition forprotecting a vehicle or other work surface to be painted or mechanicallyprocessed. For example, certain regions of an automobile may be maskedin accordance with the present invention to protect those regions frompaint overspray in a painting booth. The method and composition producesa film which adheres well to a surface to be protected, with few or nopinholes. Further, the material can be removed easily from the surfaceto be protected after use with a water wash, or by peeling, or bycombinations of the two.

More generally, the present invention provides an improved method andcomposition for protecting selected surfaces during selected mechanicalprocessing operations such as welding or grinding, as well as painting.The adherent film of the present invention protects the selected surfacefrom marring, scratching or other deleterious effects associated withmechanical processing. The mechanical processing steps might beencountered, for example, during assembly or repair of vehicles, orduring construction or renovation of buildings. The present inventioncan be employed with particular advantage during fabrication of vehiclesor other products on an assembly line. An assembly line productiontypically employs a series of steps including, for example, grinding,welding, and painting. Each of these operations can advantageouslyemploy the masking composition and method of the present invention.

One embodiment includes water, an aliphatic polyol, alcohol, and asurfactant. According to preferred embodiments, the composition includesat least about 1% polyvinyl alcohol by weight. Preferred compositionsinclude between 1 and 30% aliphatic polyol such as polyvinyl alcohol,with most preferred compositions of about 5 to 20% polyvinyl alcohol,and one specific embodiment including about 8% polyvinyl alcohol. Thealiphatic polyol component may include two different polyols havingdifferent molecular weight ranges. For example, DuPont Corporation'sElvanol 5105 (15,000 to 27,000 daltons) and Elvanol 5042 (70,000 to100,000 daltons) can be used together in some formulations.

For some applications, it will be necessary to provide a "thicker" ormore viscous protecting material formulation. For instance, in paintingtrain boxcars, a thicker formulation is desirable for protecting thewheels and couplings from overspray. The wheels and couplings of boxcarsmust be periodically inspected for cracks by techniques which are wellknown in the art. To avoid obscuring these cracks, the protectingmaterial should be thick enough that it does not penetrate any existingcracks. For such applications, the protecting material formulation maybe made thicker by a variety of means which are well known in the art.For example, the concentration of a high molecular weight polyvinylalcohol can be increased. Preferably, the masking material will have aviscosity of about 50 to 1000 centipoise, and preferably about 200centipoise.

It has been found that for general purposes a superior masking materialincludes water, an aliphatic polyol (preferably a partially hydrolyzedpolyvinyl alcohol having a molecular weight from about 15,000 to about100,000), a plasticizer, alcohol, and a surfactant. According topreferred embodiments, the composition includes at least about 0.1% byweight of a plasticizer such as glycerine. Preferred compositionsinclude between 0.5 and 7% glycerine, and one specific embodimentincluding about 1% glycerine.

An alternative preferred embodiment includes water, triethylene glycol,an aliphatic polyol, alcohol surfactants. According to this embodiment,the composition includes as a plasticizer at least about 0.1% by weighttriethylene glycol. More preferably, the triethylene glycol contentranges from 0.5% to 5%, and in one specific embodiment includes about 2%triethylene glycol. For some applications, a polyethylene glycol havinga molecular weight of between about 100 and 1,000 may be substituted asa plasticizer for the triethylene glycol.

The masking material will include a lower molecular weight alcohol.Preferred alcohols for the composition include methyl alcohol, ethylalcohol, and 2-propyl alcohol. A most preferred alcohol is ethylalcohol. For many applications, the percentage of alcohol utilized ispreferably less than about 25% by weight (based on 190-proof alcohol),with compositions having less than 20% alcohol most preferred. Whenethyl alcohol is utilized, most preferred compositions include between10 to 20% alcohol with about 10 to 15% preferred, and 12 to 13% mostpreferred. However, when thicker formulations are desired, a higherconcentration of alcohol may be used to speed the drying process. Up toabout 40% alcohol can be used for some applications. When methyl orpropyl (such as isopropyl or 2-propyl) alcohol is utilized as adenaturant, compositions with less than 1.0% by weight denaturantalcohol are preferred, and compositions of between 0.5 and 1.0% are mostpreferred.

The masking material also includes a surfactant. The surfactant is, inone embodiment, a nonionic biodegradable surfactant such as anacetylenic diol. In preferred embodiments, the invention includes analkyl aryl surfactant (such as Triton CF-10 and CF-12), a polyethoxyadduct, or a modified (poly) ethoxylate (such as Triton DF-12 andDF-16). Other surfactants include nonylphenoxypolyethanol (such asIGEPAL CO-660 made by GAF), polyoxyalkylene glycol (such as Macol 18 and19 made by Mazer Chemicals), acetylenic diol-based surfactants (such asSurfynol 104A made by Air Products), and the like. Preferredcompositions include up to 10% surfactant. Most preferred compositionsinclude less than 5% by weight surfactant and more preferably less than1% surfactant, with one specific implementation including about 0.3%surfactant.

The mask also includes a substantial amount of water, such as deionizedwater having a resistivity of about 18 megaohm-cm. In one embodiment ofthe invention, the balance of the mask is composed of water, although avariety of other materials may also be included such as dyes, odorants,and the like.

Antistatic compounds are added in preferred embodiments to reduce staticbuild-up. This prevents static from being drawn to the vehicle inquestion. Antistatics (such as Lowstat HTS-905 made by Mazer Chemicals)are provided in some embodiments, preferably water soluble.Sequesterants are also added in some embodiments (less than 1%) such ascitric acid for a pH of 5-6, glycolic, sodium citrate or the like.Sequesterants will reduce spotting.

The masking material is made by conventional means, typically includingthe steps of gently mixing the components of the masking material atsubstantially atmospheric pressure, so as to form a substantiallyhomogeneous mixture. The components are preferably heated during mixingsuch as from 180° F. to 200° F., excluding the alcohols, which are addedafter mixing the remaining components.

The masking material is applied by one of a variety of techniques.Preferred techniques include brushing and spraying of the material. Inone preferred embodiment the surface to be protected is blown dry ofdust and debris. In some cases, additional water may be added for easierapplication, such as a 10% dilution. Thereafter, the masking material isapplied with a pressure pot sprayer, preferably first in a thin mistand, thereafter, in a flow coat or thicker substantially continuousfilm. For some applications, the mist coat will not be necessary. Themask material is sprayed primarily on the surface to be protected,although overspray will not pose significant problems since anyoverspray may be readily removed with, for example, a wet towel orsponge. In preferred embodiments, the resulting masking coating is fromabout 0.5 to 4 mils thick, preferably about 1.5 to 2.5 mils thick, witha preferred thickness of about 2 mils.

The masking material is then permitted to dry, normally at atmospherictemperatures and pressures. Such drying will take about 10 to 30 minutesin typical applications (at room temperature and 30% humidity).Significantly longer drying times are needed at 50° F. For such lowertemperatures, additional ethanol may be provided in a separate containerto increase the ethanol content by about 10% by weight. The surface isthen painted or otherwise mechanically processed without fear ofoverspray on the portions of the surface protected by the maskingmaterial. Baking (at, e.g., 130° F.) may be desirable in someembodiments.

If the processing operation includes painting, the paint is firstallowed to thoroughly dry. Such drying times will vary radicallydepending upon the particular type of paint utilized. After drying ofthe paint, the masking material is removed from the protected surface.Such removal operations may include, for example, peeling of thematerial off of the protected surface. In alternative embodiments themask is removed by normal washing with water, but pressure washing withwater may be desired in some instances. The material will be removedreadily since it is easily miscible or soluble in water.

EXAMPLES

The following examples are offered as illustrations of the invention:

1. Alcohol Content

Four samples of masking material were made including 6 to 9% polyvinylalcohol, about 0.3% surfactant, and water. Varying amounts and types ofalcohols were utilized. Alcohols included ethanol, isopropanol, andmethanol. Automotive surfaces were masked with the materials. The testsshowed that while higher percentages of alcohol produced faster dryingmask materials and better layout of the materials, automotive paintswere adversely effected, resulting in dulling of the paint. Isopropyland methyl alcohols were found to have the most deleterious impact onautomotive paint. Ethyl alcohol contents of from 10 to 20% did notresult in paint damage, while having suitable drying times (about 30minutes, with the higher alcohol content samples having shorter dryingtimes), and solids dispersion properties. Using methyl and propylalcohol as denaturants, it was necessary to maintain the denaturantalcohol content below 1% of the total masking finished product to reducepaint damage to an acceptable level. Lower alcohol content may also bedesirable to ensure a higher flash point material.

2. Surfactant

Base samples with 8% polyvinyl alcohol and ethyl alcohol contentsranging from 10 to 25% were prepared. Multiple surfactants were usedincluding acetylenic diol-based surfactants (such as TG and PC made byAir Products), polyoxyalkylene glycol-based surfactant (Macol 18 and 19made by Mazer Chemicals), nonylphenoxypolyethanol-based surfactant, andpolysiloxane. 0.3% surfactant was utilized. Acetylenic diol-basedcompounds produced satisfactory results (i.e., no spotting or dulling).Polyoxyalkylene glycol-based materials produced the best results, butsuffered from foaming during application. Glycol-based compounds laidout the best overall.

3. Scents

Samples were tested to determine if an odorant would be needed toovercome effects of the high alcohol content. It was found that scentdid not appreciably improve the odor of the material when alcoholcontent was maintained below 20% and that the material had a pleasantsmell.

4. Defoamers

Samples were tested with various defoamers. Samples were tested withpolysiloxane (XFB41-58 made by Air Products), acetylenic glycol(Surfynol 64A made by Air Products), and oil-based defoamers in anamount of less than 1%, and preferably 0.05%. Polysiloxane andacetylenic glycol produced satisfactory masking material. Oil-baseddefoamers left an oily residue on protected surfaces. Acetylenic glycoldefoamer was preferred.

5. Film Prevention

In order to reduce residual films left by the masking materials,additional surfactants were tested. Alkyl aryl-based surfactants (TritonCF-10 and CF-12 or Perform Plus), polyethoxy adduct-based surfactants,and modified ethoxylate-based surfactants (such as Triton DF-12 andDF-16) were tested for residual film prevention. Polyethoxy adduct-basedsurfactants and modified ethoxylate-based surfactants provided reducedfilm retention. Particularly good results were obtained using Fluorad171 and Fluorad 430 (both made by 3M Company) in conjunction with TritonDF-16.

According to a preferred embodiment, the masking material included thefollowing components presented in a per weight basis:

Deionized water (Megaohm-cm) 79%

PVA, partially hydrolyzed solids, (typically 87%-89% hydrolyzed)

Ethyl alcohol 12.5% (including methanol; 3-6%; isopropyl of the ethanoland 1-3% of the ethanol isopropyl)

Surfactant, Perform Plus, 0.3%

Antistatic, less than 0.5%

Defoamer, less than 1%

According to a different preferred embodiment, the masking materialincluded the following components presented in a per weight basis:

Deionized water (18 ppm) 77.1%

Triethylene glycol 2.0%

Denatured ethyl alcohol 12.5%

Surfactant 0.25%

Polyvinyl alcohol (Elvanol 5042 (Dupont Corp.) 1.0% and Elvanol 5105(Dupont Corp.) 7.0% )

According to a most preferred embodiment, the masking material includedthe following components:

Deionized Water (18 ppm) 78.1%

Glycerine 1.0%

Denatured Ethyl Alcohol 12.0%

Surfactant 0.25%

Polyvinyl Alcohol (Elvanol 5042 (Dupont Corp.) 1% and Elvanol 5105(Dupont Corp.) 7%)

A thicker masking material included the following components presentedin a per weight basis, especially for use in train masking operationsand the like:

Deionized Water 49.71%

Denatured Ethyl Alcohol (190 proof) 35.00%

Glycerine 5.00%

Polyvinyl Alcohol (Elvanol 5042 (DuPont Corp.) 2.66% and Elvanol 5105(DuPont Corp.) 7.33%)

Surfactant 0.25% (Triton DF-16 0.20%, 3M FC 171 0.03%, and 3MFC 4300.02%)

Yellow Dye 0.05%

The above description is illustrative and not restrictive. Manyvariations of the invention will become apparent to those of skill inthe art upon review of this disclosure. Merely by way of example, whilethe invention is illustrated with regards to particular brands ofmaterials used in the mask, the invention is not so limited. The scopeof the invention should, therefore, be determined not with reference tothe above description, but instead should be determined with referenceto the appended claims along with their full scope of equivalents.

What is claimed is:
 1. A composition comprisinga) greater than 5% polyvinyl alcohol by weight; b) less than 20% ethyl alcohol by weight, based on 190-proof ethyl alcohol; c) less than about 1% of a surfactant by weight; d) less than about 1% of a denaturant by weight; e) less than about 1% of a polysiloxane defoamer by weight; and f) water, with the proviso that each of components (b), (c), (d) and (e) are present. 